A flat grind takes the blade down in a straight, even taper. A full flat grind starts at the spine; a high flat grind starts just below it. It is the most efficient general-purpose slicing geometry.
Because the taper is constant, there is progressively less steel the closer you get to the edge, and nothing bulges out to wedge material apart. Food, rope, cardboard and hide all separate cleanly.
Full flat grinds are standard on kitchen knives and on most modern EDC folders for exactly this reason.
Because so much steel is removed, a full flat grind leaves less mass behind the edge than a sabre grind. On a chopper or a batoning knife, that is strength you actually wanted.
It also takes longer to sharpen back to thin once the secondary bevel has widened, because there is a lot of flat surface to work.